1. Technical Field
This invention relates to a cotton expansin promoter encoding sequence, and its use in contructs useful in modifying cotton fiber phenotypes.
This invention particularly relates to methods of using in vitro constructed DNA transcription or expression cassettes capable of directing fiber-tissue transcription of a DNA sequence of interest in cotton to produce fiber cells having an altered phenotype, and to methods of providing for or modifying various characteristics of cotton fiber as well as the modified cotton fibers produced by the method.
2. Background
In general, genetic engineering techniques have been directed to modifying the phenotype of individual prokaryotic and eukaryotic cells, especially in culture. Plant cells have proven more intransigent than other eukaryotic cells, due not only to a lack of suitable vector systems but also as a result of the different goals involved. For many applications, it is desirable to be able to control gene expression at a particular stage in the growth of a plant or in a particular plant part. For this purpose, regulatory sequences are required which afford the desired initiation of transcription in the appropriate cell types and/or at the appropriate time in the plant""s development without having serious detrimental effects on plant development and productivity.
It is therefore of interest to be able to isolate sequences which can be used to provide the desired regulation of transcription in a plant cell during the growing cycle of the host plant.
One aspect of this interest is the ability to change the phenotype of particular cell types, such as differentiated epidermal cells that originate in fiber tissue, i.e. cotton fiber cells, so as to provide for altered or improved aspects of the mature cell type. Cotton is a plant of great commercial significance. In addition to the use of cotton fiber in the production of textiles, other uses of cotton include food preparation with cotton seed oil and animal feed derived from cotton seed husks.
Despite the importance of cotton as a crop, the breeding and genetic engineering of cotton fiber phenotypes has taken place at a relatively slow rate because of the absence of reliable promoters for use in selectively effecting changes in the phenotype of the fiber. In order to effect the desired phenotypic changes, transcription initiation regions capable of initiating transcription in fiber cells during development are desired. Thus, an important goal of cotton bioengineering research is the acquisition of a reliable promoter which would permit expression of a protein selectively in cotton fiber to affect such qualities as fiber strength, length, color and dyability.
Cotton fiber-specific promoters are discussed in PCT publications WO 94/12014 and WO 95/08914, and John and Crow, Proc. Natl. Acad. Sci. USA, 89:5769-5773, 1992. cDNA clones that are preferentially expressed in cotton fiber have been isolated. One of the clones isolated corresponds to mRNA and protein that are highest during the late primary cell wall and early secondary cell wall synthesis stages. John and Crow, supra.
Agrobacterium-mediated cotton transformation is described in Umbeck, U.S. Pat. Nos. 5,004,863 and 5,159,135 and cotton transformation by particle bombardment is reported in WO 92/15675, published Sep. 17, 1992. Transformation of Brassica has been described by Radke et al. (Theor. Appl. Genet. (1988) 75;685-694; Plant Cell Reports (1992) 11:499-505.
The invention provides a cotton (Gossypium hirsutum) promoter region from an expansin gene expressed in developing fiber. Novel DNA promoter sequences are supplied, and methods for their use are described for directing transcription of a gene of interest in cotton fiber using the promoter region from an expansin gene which is expressed in cotton fiber.
In efforts to identify genes critical to fiber development, we have initiated a program sequencing randomly selected cDNA clones derived from a library prepared from mRNA harvested from fibers at the stage in which secondary wall synthesis approaches its maximum rate (approximately 21 dpa).
We have characterized a cotton (Gossypium hirsutum) cDNA clone which is a homolog of the expansin gene. The sequences of this cDNA clone is homologous to that of other expansin encoding sequences The 5xe2x80x2 genomic promoter region from this gene has been sequenced for approximately 2200 base pairs.
Thus, the application provides sequences and methods of use relating to modification of phenotype in cotton fiber using a promoter of the cotton expansin gene.